Get network_3GModemControl working with shill.

- Fix mis-capitalization in "LastGoodAPN" property.
- Switch to Device.Enable()/Disable() instead of "Powered" property.
- Increase timeout waiting for cellular service to enter a specific
  state.
- Add additional debug tags to help debug failures.

BUG=chromium-os:25566
TEST=network_3GModemControl

Change-Id: Ifd097950dfc918c78c1daba7776600ed12bf977c
Reviewed-on: https://gerrit.chromium.org/gerrit/22760
Reviewed-by: Jason Glasgow <jglasgow@chromium.org>
Tested-by: Thieu Le <thieule@chromium.org>
Reviewed-by: Thieu Le <thieule@chromium.org>
Commit-Ready: Thieu Le <thieule@chromium.org>
2 files changed